Thermostatic cutoff electric switch



July 15, 1941. J ADAMS 2,248,928

THERMOSTATIC CUTOFF ELECTRIC swmca Filed Aug. 28, 1940 2 She etS-Sheet 1 In uentor u 26 By A ttorney July 15, 1941. ADAMS 2,248,928

THERMOSTATIG CUTOFF ELECTRIC SWITCH Filed Aug. 28, 1940 2 Sheets-Sheet 2 W A A 6: Inventor I. J54 ,1" 44m"; 11 Q By Q 406: M

Aiiornel,

Patented July 15, 1941 oFFicE THERMOSTATI C CUTOFF ELECTRIC SWITCH John F. Adams, Jacksonville, Fla, assignor of one-half to W. K. Drake, Jacksonville, Fla.

Application August 28, 1940, Serial No. 354,6t5

(Cl. Hill- 139) 3 Claims.

This invention relates to an automatic cutoff electric switch. The primary object of this invention is to provide a device of the above stated character which may be successfully employed for the cutting off of electric circuits on various devices, one of the many uses in which this device may he employed is to automatically break an electric circuit when the water within a tank or container, which is electrically heated for domestic purposes, reaches a predetermined tem perature and remains in circuit-breaking position until manually restored, thereby providing a safety device which will eliminate the careless leaving on of the electric heater for too long a period of time as would raise the temperature of water to become dangerous.

With these and other objects in view as will become more apparent as the description proceeds, the invention consists in certain novel features of construction, combination and arrangement of parts as will be hereinafter more fully described and claimed.

For a complete understanding of my invention, reference is to be had to the following description and accompanying drawings, in which Figure 1 is a front elevation, partly in section, illustrating an automatic cutoff electric switch constructed in accordance with my invention.

Figure 2 is a rear elevation illustrating the device.

Figure 3 is a transverse sectional view illus- 'irating the device.

Figure 4 is a plan view, partly in section,illustrating the thermostatic element and its mountlng.

Figure 5 is a side elevation illustrating an adapter for the mounting of this invention on a Water container or tank or some other similar device.

Figure 6 is a top plan view partly in section illustrating a modified form or mounting of the present invention on the tank or container.

Figure 7 is a perspective View illustrating a setting lever.

Figure 8 is a perspective view illustrating an eccentric for the thermostat element.

Figure 9 is a detail sectional view illustrating the driving lugs between the thermostat element and the switch arm.

Referring in detail to the drawings, the numeral 5 indicates a casing composed of sections 6 and l detachably connected by stud bolts 8. Slots 9 and I 0 are formed in opposite walls of the casing through which extends a setting lever H and a switch arm l2.

The rear wall of the casing may be mounted on a tank or container as shown in Figure 3 or Figure 6. When mounted on the tank: or container which is indicated by the character 53, as shown in Figure 3, the rear wall has formed thereon an internally screw threaded boss it in which is threaded an adapter iii. The adapter threads into an opening provided in the tank or container to permit the water thereof to contact a portion of the rear wall.

When the device is adapted to a container or tank, as shown in Figure 6, the rear wall is curved, as shown at it, so as to readily conform to the contour of the tank or container. In this instance, the casing 5 has formed thereon apertured ears ii to which an anchoring element 63 is connected after encircling the tank or contamer.

The switch arm l2 has a finger piece l9 and the setting lever H has a finger piece 20 movable over the exterior walls of the casing, as clearly shown in Figure 3, as well as in Figure 1. The front wall of the casing or that part over which the finger piece is of the switch arm moves is provided with off and on positions for the switch arm and arranged between said positions is a scale denoting temperatures. The front wall of the casing is further provided with a temperature scale on that part over which the finger piece 20 of the setting lever ll moves.

A stud 20' is located centrally of the casing and is secured to the rear wall thereof and has journaled thereon a sleeve 2! to which the inner end of a spirally formed thermostatic element 22 is secured. The, outer end of said thermostatic element is in the form of an eye mounted on an eccentric 23 journaled in the casing. The purpose of the eccentric is to provide an adjustment for the accuracy of the scales provided on the switch casing to overcome manufacturing variations. The thermostatic element 22 is of the bimetallic construction, as clearly shown in Figure 4 as well as in Figure 3.

The sleeve 2| has formed thereon a lug 25 and located within the path of the lug 25 is a lug 26' formed on a sleeve 21 journaled on the stud 20' and forming an integral part of the switch arm l2. The setting lever is carried by the stud 20' with a portion overlapping the switch lever and is arranged to have free movement with relation to the stud as well as to the switch lever.

Lugs 26 and 21 are formed on the setting lever II and the switch arm l2 and are connected by a coil spring 28. It will be noted that the setting lever extends in an opposite direction to the switch arm, as shown in Figure 1, so that when the switch arm is in an off position and the setting lever is placed for the highest temperature reading on the scale, the coil spring extends directly across the stud However, when the switch arm is moved to on position with the setting lever placed opposite a selected temperature reading on the casing the spring 28 will then be located to one side of the stud 20' so that the spring acts to retain the switch arm in on position.

As the water is heated in the container or tank it acts on the thermostat element and as the latter expands or uncoils the lug abuts the lug 26 and imparts movement to the switch arm towards off position and when the water reaches a temperature at which the setting lever is positioned the coil spring then will have moved to the opposite side of the stud bolt and any further movement caused by the thermostatic element will cause the coil spring to exert a pull on the switch arm to move the same into a full off or circuit-breaking position. The spring acts to retain the switch arm in the off position until it is manually moved into on position.

The purpose of the temperature scale in conjunction with the switch arm is to indicate the gradual rise in temperature of the water by the movement of the switch arm in relation to said scale.

Operating in conjunction with the switch arm are mercury type tubes 30 secured by brackets 3| to the switch arm and when the latter is in an off position said tubes are disposed in such a position that the mercury thereof will not bridge both contacts at one end of the tubes. However, when the switch arm is moved to on position the mercury tubes are tilted from their normal position so that the mercury will bridge the contacts at one end of said tubes.

An extension 32 is integral with the casing in which a terminal bridge 33 is mounted for the connecting of the conductors of the contacts of the mercury tubes to conductors forming an electric circuit which extends outwardly of the extension 32 by way of an opening 34 provided therein.

The operation of this device is extremely simple. The absorption of heat by the thermostatic element causes the inner end to rotate in a clockwise direction. When the ing 25 engages the lug 26, the switch B is caused to rotate in a corresponding direction until it reaches the dead center point with respect to the spring 28 beyond which the spring will carry the switch arm to its extreme off position. On any reduction in temperature the thermostatic element causes a reverse movement of the lug 25 but will not affect the position of the switch arm which will remain in its off position until it is again moved into an on position manually. As long as the switch arm is in on position, the finger piece thereof will vary with respect to the temperature scale on the casing and therefore will denote when the heater is in operation and the temperature of the water rising so that a. person may readily determine the temperature of the water within the tank or container.

1. In a switch of the character described, a

casing, means for connecting said casing to a liquid container, a switch arm operable in said casing and extending exteriorly thereof and having 011 and on positions with a temperature scale therebetween viewable from the exterior of the casing, a setting lever pivotally mounted in said casing with its pivot common to the pivot of said switch lever and extending exteriorly of the cas ing and movable over a temperature scale visible from the exterior of said casing, a mercury type switch operable by the movement of the switch arm into circuit making and breaking positions, spring means connecting the switch arm to the setting arm, and a thermostat means for moving the switch arm toward of! position and without power to return the switch arm toward on position.

2. In a switch of the character described, a casing, a switch arm pivoted in said casing and extending exteriorly thereof and movable over a temperature scale viewable on the casing from the exterior thereof, a setting lever pivoted in said casing with its pivot common to the pivot of said switch arm and extending exteriorly of the casing and movable over a temperature scale visible on said casing from the exterior thereof, a mercury switch connected with said switch arm, a tension spring connecting the setting lever to the switch arm and movable relative to the pivots of said arm and lever, a thermostatic means for moving the switch arm toward off position and without power to return the switch arm toward on position.

3. In a switch of the character described, a casing, a switch arm pivoted in said casing and extending exteriorly thereof and movable over a temperature scale viewable on the casing from the exterior thereof, a setting lever pivoted in said casing with its pivot common to the pivot of said switch arm and extending exteriorly of the casing and movable over a temperature scale visible on said casing from the exterior thereof, a mercury switch connected with said switch arm, a tension spring connecting the setting lever to the switch arm and movable relative to the pivots of said arm and lever, a sleeve journaled in said casing with its journal common to the pivots of said arm and lever, a lug formed on said sleeve, a coil type thermostatic element located in said casing and having one end connected to said sleeve, an eccentric'means connecting the other end of the thermostatic element to the casing for the adjustment of the latter, a second'sleeve connected to the switch arm, and 8. lug formed on the second sleeve and located within the path of the first lug.

JOHN F. ADAMS. 

